Vibration isolator

ABSTRACT

A vibration isolator comprises: a first member in which an end portion of a shaft portion being fixed to a mating member; a vibration-isolation base made of an elastic body connecting a second member and the first member; and a stopper made of an elastic body arranged between the second member and the mating member with the first surface. The shaft portion is arranged in the hole of the stopper with the end portion facing the matching member. The inner surface of the hole of the stopper, prior to the shaft portion is inserted into the hole, includes: a first portion having a span smaller than the thickness of the end portion of the shaft portion; and a second portion arranged between the first portion and the second surface. A span of the second portion is greater than the span of the first portion.

TECHNICAL FIELD

The present invention relates to a vibration isolator comprising astopper.

BACKGROUND ART

Patent Literature 1 discloses a vibration isolator comprising: a firstmember being fixed to a mating member, such as a power unit; a secondmember spaced from the first member; a vibration-isolation base made ofan elastic body connecting the second member and the first member; and astopper made of the elastic body through which the shaft portionpenetrates, wherein the stopper is arranged between the second memberand the mating member. In this type of the vibration isolator, thestopper is interposed between the mating member and the second member tomitigate collisions between the mating member and the second member. Thestopper is fixed to the shaft portion using friction between the stopperand the shaft portion so that the stopper does not detach from the shaftportion prior to the first member being fixed to the mating member.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Patent No. 5568472

SUMMARY OF INVENTION Technical Problem

Unfortunately, if friction between the hole of the stopper and the shaftportion is increased, the stopper can be less likely to detach from theshaft portion. This makes it difficult to insert the shaft portion intothe hole of the stopper in manufacturing process of the vibrationisolator. While, if friction between the hole of the stopper is reduced,the shaft portion can be easily inserted into the hole of the stopper inthe manufacturing process of the vibration isolator. This causes thestopper to be likely to detach from the shaft portion prior to thevibration isolator being fixed to the mating member.

It is an object of the present invention to provide a vibration isolatorconfigured such that a shaft portion can be easily inserted into a holeof a stopper and a stopper can be less likely to detach from the shaftportion.

Solution to Problem

A vibration isolator of the present invention to achieve this objectincludes a first member, a second member, a vibration-isolation base,and a stopper made of an elastic body. The first member comprises ashaft portion extending along the axis line, an end portion of the shaftportion being fixed to a mating member. The second member is spaced fromthe first member and at least a portion of the second member is spacedfrom the shaft portion perpendicular to the axis line. Thevibration-isolation base is made of an elastic body connecting thesecond member and the first member. The stopper includes a first surfaceand a second surface on the other side of a first surface. The stopperis arranged between the second member and the mating member: the firstsurface of the stopper is directed to the mating member; the secondsurface of the stopper is directed to the second member. A hole of thestopper connects the first surface and the second surface. The shaftportion is arranged in the hole of the stopper with the end portionfacing the matching member. The inner surface of the hole of the stopperincludes: a first portion; and a second portion arranged between thefirst portion and the second surface. Prior to the shaft portion beingarranged in the hole of the stopper, the span of the first portion issmaller than the end portion thickness of the shaft portion, and thespan of the second portion is greater than the span of the firstportion.

Advantageous Effects of Invention

With the vibration isolator according to a first aspect, when the shaftportion is inserted from the second surface of the stopper into the holeof the stopper, the end portion of the shaft portion reaches the secondportion and then reaches the first portion. The span of the firstportion is smaller than the end portion thickness of the shaft portion.Therefore, in a state where the shaft portion is inserted into the holeof the stopper, the stopper can be less likely to detach from the shaftportion due to friction between the shaft portion and the first portion.The span of the second portion is larger than the span of the firstportion. Therefore, when the shaft portion is inserted into the hole ofthe stopper, the shaft portion spreads the first portion connecting thesecond portion. This ensures the shaft portion can be easily insertedinto the hole of the stopper. Accordingly, the shaft portion can beeasily inserted into the hole of the shaft portion and the stopper canbe less likely to detach from the shaft portion.

With the vibration isolator according to a second aspect, the firstportion is in contact with the shaft portion in a state the shaftportion is arranged in the hole of the stopper. This ensures the stoppercan be much less likely to detach from the shaft portion due to frictionbetween the inner surface of the hole and the shaft portion, in additionto the effects of the first aspect.

With the vibration isolator according to a third aspect, the firstportion includes the entire periphery of the inner surface of the hole.Accordingly, the stopper can be much less likely to detach from theshaft portion, in addition to the effects of the second aspect.

With the vibration isolator according to a fourth aspect, the stopperhas a convex portion raised from at least a portion of the first surfacearound the hole in the direction of the axis line. The first portionincludes inside the elastically deformable convex portion. Accordingly,the shaft portion can be more easily inserted into the hole of the shaftportion, in addition to the effects of the first aspect.

With the vibration isolator according to a fifth aspect, the stopperincludes a step between the first portion and the second surface, andthe second portion is disposed between the step and the second surface.In a state where the shaft portion arranged in the hole of the stopper,the second portion is spaced from the shaft portion so that when a forcetoward the end portion of the shaft portion is applied to the stopper,the stopper bends at the step and the stopper is less likely to movetoward the end portion of the shaft portion. Accordingly, the stoppercan be much less likely to detach from the shaft portion, in addition tothe effects of the fourth aspect.

With the vibration isolator according to a sixth aspect, in a stateprior to the shaft portion being arranged in the hole, the span of thesecond portion is larger than the end portion thickness of the shaftportion. Accordingly, the shaft portion can be more easily inserted intothe hole of the shaft portion, in addition to the effects of the firstaspect.

With the vibration isolator according to a seventh aspect, the span ofthe inner surface increases from the first portion to the second portionin a state prior to the shaft portion being arranged in the hole.Accordingly, the shaft portion can be more easily inserted into the holeof the shaft portion, in addition to the effects of the first aspect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a vibration isolator in a firstembodiment;

FIG. 2 is a cross-sectional view including the axis line of a stopper.

FIG. 3 is a plan view of the stopper as viewed in the direction of ArrowIII in FIG. 2.

FIG. 4 is a plan view of a stopper of the vibration isolator accordingto a second embodiment.

FIG. 5 is a cross-sectional view of a stopper of the vibration isolatoraccording to a third embodiment.

FIG. 6 is a cross-sectional view of a stopper of the vibration isolatoraccording to a fourth embodiment.

FIG. 7 is a cross-sectional view of a stopper of the vibration isolatoraccording to a fifth embodiment.

FIG. 8 is a cross-sectional view of the vibration isolator according toa sixth embodiment.

FIG. 9 is a cross-sectional view including the axis line of a stopper.

DESCRIPTION OF EMBODIMENTS

The following describes preferable embodiments of the present inventionwith reference to the attached drawings. FIG. 1 is a cross-sectionalview of a vibration isolator 10 according to a first embodiment. Thevibration isolator 10 is a liquid-sealed vibration isolator whichelastically supports a power unit such as an engine of a motor vehicle.FIG. 1 illustrates the vibration isolator 10 with no differentialpressures between a main fluid chamber 36 and a sub-liquid chamber 37(described later).

As illustrated in FIG. 1, the vibration isolator 10 comprises: a firstmember 11 and a second member 20 spaced from each other in the directionof the axis line O; a vibration-isolation base 30 connecting between thefirst member 11 and the second member 20; and a stopper 40 fixed to thefirst member 11. In the present embodiment, the first member 11 is fixedto a mating member 16 (brackets in the present embodiment) attached to apower unit (not illustrated) which is a vibration source, and the secondmember 20 is attached to a vehicle body frame (not illustrated). In thepresent embodiment, the axis line O of the vibration isolator 10coincides with the vertical line.

The first member 11 is an integrally formed metallic member such as aniron-based material or an aluminum alloy. The first member 11 includes:a disk-shaped base 12 connected the vibration-isolation base 30; and ashaft portion 13 connected to the center of the base 12. The shaftportion 13 is a cylindrical part extending along the axis line O. Ascrew hole 15 is formed in the center of the shaft portion 13 along theaxis line O. The screw hole 15 opens into an end portion 14 located onthe other side of the base 12. In the present embodiment, the outerperipheral surface of the shaft portion 13 is formed in a tapered shapewhose diameters gradually decrease toward the end portion 14. The shaftportion 13 is attached to the mating member 16, in a state where the endportion 14 is abutted against the mating member 16, using a bolt 17attached to the screw hole 15.

A second member 20 is a cylindrical metallic member extending along theaxis line O. The second member 20 includes a cylindrical body 21, anannular body 22, and a bottom member 24. The cylindrical body 21 is acylindrical member having an inner diameter larger than the diameter ofthe base portion 12. The vibration-isolation base 30 is bonded to theinner peripheral surface of the cylindrical member 21. The annular body22 is an annular member fixed to the cylindrical body 21. The annularbody 22 has a displacement-regulating portion 23. Thedisplacement-regulating portion 23 is a portion arranged around theshaft portion 13. A gap is formed between the displacement-regulatingportion 23 and the shaft portion 13. The displacement-regulating portion23 has a portion opposed to the base portion 12 in the direction of theaxis line. The bottom member 24 is a bottomed cylindrical member fixedto the cylindrical body 21, and is arranged on the opposite side of theannular body 22.

A vibration-isolation base 30 is made of a substantially frusto-conicalelastic body, such as rubber or thermoplastic elastomer, and connectsthe base 12 and the cylindrical body 21. In the present embodiment, thevibration-isolation base 30 is made of rubber and is vulcanized andbonded to the base 12 and the cylindrical body 21. In thevibration-isolation base 30, a membrane portion 31 is integrally molded.The membrane portion 31 is provided on the surface of the base portion12 on the side of the displacement-regulating portion 23. The membraneportion 31 is interposed between the displacement-regulating portion 23and the base portion 12.

A diaphragm 32 is a substantially circular flexible membrane made of anelastic body, such as rubber or thermoplastic elastomer. An annularfixing member 33 is bonded to the outer peripheral edge of the diaphragm32. The fixture 33 is sandwiched between the cylindrical body 21 and thebottom member 24 over the entire circumference. Liquid such as water andethylene glycol are sealed between the diaphragm 32 and thevibration-isolation base 30. A partition 34 is arranged between thediaphragm 32 and vibration-isolation base 30. The partition 34 forms anorifice 35 and partitions between the diaphragm 32 and thevibration-isolation base 30. Accordingly, a main liquid chamber 36 and asub-liquid chamber 37 are formed. The orifice 35 communicates the mainliquid chamber 36 and the sub-liquid chamber 37.

The vibration isolator 10 is tuned such that the orifices resonates whenlarge-amplitude vibrations, such as engine shakes, are entered.Therefore, when a large-amplitude vibration is inputted into thevibration isolator 10 and a pressure difference is generated between themain liquid chamber 36 and the sub-liquid chamber 37, the liquid flowsbetween the main liquid chamber 36 and the sub-liquid chamber 37 throughthe orifices 35, and the vibration is damped.

A stopper 40 is made of an elastic body such as rubber or thermoplasticelastomer. The stopper 40 is integrally formed with a substantiallycircular main body 41 arranged between the mating member 16 and thedisplacement-regulating portion 23, and a cylindrical side wall 42extending along the axis line O from the outer peripheral edge of themain body 41. The side wall 42 is arranged outside the annular body 22.The stopper 40 is attached to the shaft portion 13, and the shaftportion 13 penetrates the body 41 of stopper 40.

FIG. 2 is a cross-sectional view of the stopper 40 including the axisline O. FIG. 3 is a plan view of the stopper 40 as viewed in thedirection of Arrow III in FIG. 2. FIGS. 2 and 3 illustrate the stopper40 prior to be attached to the shaft portion 13. In FIG. 2, the shaftportion 13 when inserted into a hole 45 of the stopper 40 is illustratedin a long dashed double-short dashed line (the same applies to FIGS. 5,6, 7 and 9). Therefore, in a state where the shaft portion 13 isactually inserted into the hole 45 of the stopper 40, the area insidethe long dashed double-short dashed line indicating the shaft portion 13and the area where the stopper 40 overlap indicate that the stopper 40is crushed.

As illustrated in FIG. 2, the stopper 40 has a first surface 43 and asecond surface 44 on the other side of the first surface 43 formed inthe main body 41. The first surface 43 is formed with concavities andconvexities, but the second surface 44 is flat. The hole 45 connectingthe first surface 43 and the second surface 44 is formed in the centerof the main body 41. The hole 45 penetrates the body 41. An innersurface 49 of the hole 45 is circular about the axis line O as in viewedin the direction of the axis line (see FIG. 3).

The first surface 43 of the main body 41 has a first stopper surface 46,a second stopper surface 47, and a third stopper surface 48. The firststopper surface 46 is the longest distance from the second surface 44and the third stopper surface 48 is the shortest distance from thesecond surface 44. The distance between the second stopper surface 47and the second surface 44 is intermediate the distance between the firststopper surface 46 and the second surface 44 and the distance betweenthe third stopper surface 48 and the second surface 44. The firststopper surface 46, the second stopper surface 47, and the third stoppersurface 48 define the load deflection curves when the stopper 40regulates the deflection of the mating member 16 in the bound direction.

The inner surface 49 of the hole 45 includes a first portion 50connected to the first surface 43, a second portion 52 connected to thesecond surface 44, and a step 51 formed between the first portion 50 andthe second portion 52. The first portion 50 is a section in which a spanD1 (the chord passing through the axis line O in this embodiment) issmaller than a diameter D3 of the end portion 14 of the shaft portion13. The second portion 52 is a portion where a span D2 is larger thanthe span D1 of the first portion 50. The first portion 50 and the secondportion 52 are cylindrical surfaces, and the step 51 is an annularsurface. The step 51 is formed at a position closer to the secondsurface 44 than the third stopper surface 48. In the present embodiment,the span D2 of the second portion 52 is larger than the diameter D3 ofthe end portion 14 of the shaft portion 13.

The body 41 of the stopper 40 has a convex portion 53 raised from thefirst surface 43 (the third stopper surface 48) around the hole 45 inthe direction of the axis line. The height of the convex portion 53 fromthe second surface 44 is higher than the height of the second stoppersurface 47 from the second surface 44 and is the same height as thefirst stopper surface 46 from the second surface 44. The convex portion53 is connected to the first stopper surface 46 (see FIG. 3). The span(diameter) of the peripheral edge of the convex portion 53 is largerthan the span (diameter) of the peripheral edge of step 51. The firstportion 50 is formed inside the convex portion 53. The first portion 50and the second portion 52 are formed over the entire circumference ofthe inner surface 49 of the hole 45.

Referring back to FIG. 1, the followings will be described. In vibrationisolator 10, the main body 41 of the stopper 40 is interposed betweenthe mating member 16 and the displacement-regulating portion 23. Theconvex portion 53 (see FIG. 2) is arranged inside thedisplacement-regulating portion 23. The stopper 40 mitigates collisionsbetween the mating member 16 and the second member 20 (thedisplacement-regulating portion 23) when a power unit (not illustrated)attached to the mating member 16 is bounced. The stopper 40 is fixed tothe shaft portion 13 being fixed to the mating member 16, due tofriction. The stopper 40 is arranged between the mating member 16 andthe second member 20. Accordingly, abnormal noise generated when thestopper 40 collides with the second member 20 or the mating member 16due to vibrations when the vehicle is traveling can be suppressed.

The shaft portion 13 is inserted into the hole 45 of stopper 40 from thesecond surface 44 of the stopper 40 when the vibration isolator 10 ismanufactured. The stopper 40 is fixed to the shaft portion 13 usingfriction between the inner surface 49 (see FIG. 2) of the hole 45 of thestopper 40 and the shaft portion 13. Therefore, prior to the firstmember 11 being fixed to mating member 16 (Prior to the vibrationisolator 10 is mounted on the vehicle), the stopper 40 does not detachfrom the shaft portion 13.

The stopper 40 may be bonded to the shaft portion 13 using a liquid orgel-like adhesive (e.g., a cyanoacrylate-based adhesive) so that thestopper 40 does not detach from the shaft portion 13 prior to the firstmember 11 being fixed to the mating member 16. However, when the shaftportion 13 is inserted into the hole 45 of the stopper 40 after anadhesive is applied to the shaft portion 13, the adhesive may flow alongthe surfaces of the shaft portion 13, so that a higher adhesive forcemay not be obtained. It is also difficult to inject an adhesive betweenthe shaft portion 13 and the stopper 40 after inserting the shaftportion 13 into the hole 45 of the stopper 40. Thus, it is difficult tobond the stopper 40 to the shaft portion 13.

In contrast, according to the stopper 40, when the shaft portion 13 isinserted from the second surface 44 side of the stopper 40 into the hole45 of the stopper 40 when the vibration isolator 10 is manufactured, theend portion 14 of the shaft portion 13 reaches the second portion 52,and then reaches the first portion 50. Since the span D1 of the firstportion 50 is smaller than the thickness (the diameter in thisembodiment) of the end portion 14 of the shaft portion 13, it ispossible to prevent the stopper 40 from being detached from the shaftportion 13 using friction between the shaft portion 13 (the end portion14) and the first portion 50 in a state where the shaft portion 13 isinserted into the hole 45 of the stopper 40 without using an adhesive.

The span D2 of the second portion 52 is larger than the span D1 of thefirst portion 50. Therefore, when the shaft portion 13 is inserted intothe hole 45 of the stopper 40, the shaft portion 13 (the end portion 14)spreads the first portion 50 connecting the second portion 52.Accordingly, the shaft portion 13 can be easily inserted into the hole45 of the stopper 40, and the stopper 40 can be less likely to detachfrom the shaft portion 13 (the end portion 14) after the shaft portion13 is inserted into the hole 45. The operation of bonding the stopper 40to the shaft portion 13 using an adhesive can also be omitted.

In a state where the shaft portion 13 is inserted into the hole 45 ofthe stopper 40, the first portion 50 is in contact with the shaftportion 13. This ensures the stopper 40 can be less likely to detachfrom the shaft portion 13 due to friction between the inner surface 49of the hole 45 and the shaft portion 13. The first portion 50 is formedover the entire circumference of the inner surface 49 of the hole 45.Accordingly, the stopper 40 can be much less likely to detach from theshaft portion 13.

The stopper 40 has the convex portion 53 raised from at least a portionof the first surface 43 around the hole 45 in the direction of the axisline. The raised convex portion 53 tends to elastically deform radiallyoutward. Since the first portion 50 is formed inside the deformable theconvex portion 53, the shaft portion 13 can be more easily inserted intothe hole 45 of the stopper 40. Since the convex portion 53 is arrangedinside the displacement-regulating portion 23, the convex portion 53does not affect the load deflection curves of the stopper 40.

The step 51 is formed between the first portion 50 and the secondsurface 44 of the stopper 40, and the second portion 52 is formedbetween the step 51 and the second surface 44. The second portion 52 isspaced from the shaft portion 13 in a state where the shaft portion 13is inserted into the hole 45 of the stopper 40, when a force toward theend portion 14 side of the shaft portion 13 is applied to the stopper40, the stopper 40 (the main body 41) bends at the step 51 and the firstportion 50 can be less likely to move toward the end portion 14 side ofthe shaft portion 13. Therefore, it is possible to make the stopper 40can be much less likely to detach from the shaft portion 13.

Since the step 51 is formed on the second surface 44 side of the thirdstopper surface 48 of the main body 41 on which the convex portion 53 israised, the volume of convex portion 53 can be made larger than when thestep 51 is formed on the first surface 43 side of the third stoppersurface 48. Therefore, the rigidity of the convex portion 53 can beincreased. As a result, the friction between the first portion 50 formedon the inner side of the convex portion 53 and the shaft portion 13 canbe secured, thereby the stopper 40 can be less likely to detach from theshaft portion 13.

With the stopper 40, prior to the shaft portion 13 is inserted into thehole 45, the span D2 of the second portion 52 is larger than thethickness of the end portion 14 of the shaft portion 13. Therefore, theshaft portion 13 can be more easily inserted into the hole 45 of thestopper 40. In addition, the outer peripheral surface of the shaftportion 13 is formed in a tapered shape whose diameters graduallydecrease toward the end portion 14. Therefore, the shaft portion 13 canbe more easily inserted into the hole 45 of the stopper 40.

The second embodiment will be described with reference to FIG. 4. In thefirst embodiment, the inner surface 49 of the hole 45 of the stopper 40has a circular shape. On the other hand, in the second embodiment, astopper 60 in which an inner surface 61 of the hole 45 is ellipticalwill be described. The same portions as those of the first embodimentwill be denoted by the same reference numerals, and the description ofsuch parts will be omitted. FIG. 4 is a plan view of the stopper 60 ofthe vibration isolator according to the second embodiment. The stopper60 is arranged in place of the stopper 40 of the vibration isolator 10in the first embodiment.

The stopper 60 is used with the shaft portion 13 inserted into the hole45 penetrating the stopper 60. The inner surface 61 of the hole 45 iselliptical around the axis line O. The inner surface 61 includes: firstportions 62 facing each other with a axis line O interposedtherebetween; third portions 63 circumferentially connected to the firstportions 62 and facing each other with a axis line O interposedtherebetween; and a second portion (not illustrated) positioned betweenthe first portion 62 and the second surface 44 (see FIG. 2). The span D4(the length of the chord passing through the axis line O) of the thirdportion 63 is larger than the thickness (diameter) of the end portion 14of the shaft portion 13. The span D1 (the length of the chord passingthrough axis line O) of the first portion 62 is smaller than thethickness (the diameter D3) of the end portion 14 of the shaft portion13. Therefore, the stopper 60 can be less likely to detach from theshaft portion 13 due to friction between the shaft portion 13 and thefirst portion 62 in a state where the shaft portion 13 is inserted intothe hole 45 of the stopper 40.

The third embodiment will be described with reference to FIG. 5. In thefirst embodiment, the height of the convex portion 53 of the stopper 40is the same as the height of the first stopper surface 46. In contrast,in the third embodiment, a convex portion 73 of a stopper 70 is higherthan the first stopper surface 46. The same portions as those of thefirst embodiment will be denoted by the same reference numerals, and thedescription of such parts will be omitted.

FIG. 5 is a cross-sectional view of the stopper 70 according to thevibration isolator in the third embodiment. FIG. 5 omits theillustration of one side of the stopper 70 bounded by the axis line O(the same applies to FIGS. 6, 7 and 9). The stopper 70 is arranged inplace of the stopper 40 of the vibration isolator 10 in the firstembodiment.

The stopper 70 is used with the shaft portion 13 inserted into the hole45 penetrating the stopper 70. When an inner surface 71 of the hole 45is viewed from the first surface (see FIG. 2) in the direction of theaxis line, the inner surface 71 is a circle centered on the axis line O.The inner surface 71 includes a first portion 72, the step 51, and thesecond portion 52 having a larger span D1 than the thickness (thediameter D3) of the end portion 14 of the shaft portion 13. The convexportion 73 having the first portion 72 formed inside is raised from thethird stopper surface 48. The height of the convex portion 73 is higherthan that of the first stopper surface 46. Since the convex portion 73is arranged inside the displacement-regulating portion 23 (see FIG. 1),the convex portion 73 does not affect the load deflection curves of thestopper 70.

The fourth embodiment will be described with reference to FIG. 6. In thefirst and the third embodiments, the step 51 is formed between the firstportions 50, 72 and second the portion 52. On the other hand, in thefourth embodiment, a first portion 82 and the second portion 83 aresmoothly connected to each other. The same portions as those of thefirst embodiment will be denoted by the same reference numerals, and thefollowing description will be omitted. FIG. 6 is a cross-sectional viewof a stopper 80 of the vibration isolator according to the fourthembodiment. The stopper 80 is arranged in place of the stopper 40 of thevibration isolator 10 in the first embodiment.

The stopper 80 is used with the shaft portion 13 inserted into the hole45 penetrating the stopper 80. When an inner surface 81 of the hole 45is viewed from the first surface 43 (see FIG. 2) in the direction of theaxis line, the inner surface 81 is a circle centered on the axis line O.In the inner surface 81, the first portion 82 and a second portion 83are smoothly connected. The first portion 82 and the second portion 83are formed conically. A convex portion 84 having the first portion 82formed inside is raised from the third stopper surface 48.

The first portion 82 is a portion in which the span D1 is smaller thanthe thickness (the diameter D3) of the end portion 14 of the shaftportion 13. The second portion 83 is a portion in which the span D2 islarger than the span Dl. The span D2 of the second portion 83 is largerthan the thickness D3 of the end portion 14 of the shaft portion 13, andthe second portion 83 is spaced from the shaft portion 13 in a statewhere the shaft portion 13 is inserted into the hole 45. Prior to theshaft portion 13 is inserted into the hole 45, the span of the innersurface 81 increases from the first portion 82 to the second portion 83.Therefore, the shaft portion 13 can be easily inserted into the hole 45of the stopper 80.

The fifth embodiment will be described with reference to FIG. 7. In thefourth embodiment, the first portion 82 and the second portion 83, whichare smoothly connected to each other, are formed in a conical shape. Onthe other hand, in the fifth embodiment, a first portion 92 formed in acylindrical shape and a second portion 93 formed in a conical shape aresmoothly connected to each other. The same portions as those of thefirst embodiment will be denoted by the same reference numerals, and thefollowing description will be omitted. FIG. 7 is a cross-sectional viewof the stopper 90 of the vibration isolator in the fifth embodiment. Thestopper 90 is arranged in place of the stopper 40 of the vibrationisolator 10 in the first embodiment.

The stopper 90 is used with the shaft portion 13 inserted into the hole45 penetrating the stopper 90. When an inner surface 91 of the hole 45is viewed from the direction of the axis line, the inner surface 91 is acircle centered on the axis line O. In the inner surface 91, the firstportion 92 and the second portion 93 are smoothly connected. The firstportion 92 is a cylindrical surface, and the second portion 93 is aconical surface that gradually increases in span toward the secondsurface 44. In the present embodiment, the second portion 93 is roundedso as to be convex radially inward. A convex portion 94 having the firstportion 92 formed inside is raised from the third stopper surface 48.

The span D1 of the first portion 92 is smaller than the thickness (thediameter D3) of the end portion 14 of the shaft portion 13. The span D2of the second portion 93 is greater than the thickness D3 of the endportion 14 of the shaft portion 13. In a state where the shaft portion13 is inserted into the hole 45, the second portion 93 is spaced fromthe shaft portion 13. Prior to insertion of the shaft portion 13 intothe hole 45, the span of the second portion increases as it approachesthe second surface 44. Therefore, the shaft portion 13 can be easilyinserted into the hole 45 of the stopper 90.

The sixth embodiment will be described with reference to FIGS. 8 and 9.In the first to fifth embodiments, the liquid-sealed vibration isolator10 using the resonant phenomena of the liquid has been described. On theother hand, in the sixth embodiment, a vibration isolator 100 using nofluid will be described. FIG. 8 is a cross-sectional view including theaxis line O of the vibration isolator 100 according to the sixthembodiment.

As illustrated in FIG. 8, the vibration isolator 100 elastically couplesa mating member 101 such as brackets attached to, for example, a vehiclebody and an arm 102 used for, for example, suspensions. The vibrationisolator 100 comprises: a first member 110; a second member 120 spacedfrom the first member 110 and surrounding the first member 110; asubstantially cylindrical vibration-isolation base 130 coupling thefirst member 110 and the second member 120; and a stopper 140 attachedto the first member 110. The second member 120 is arranged radiallyoutward of the first member 110. A vibration-isolation base 130 is madeof an elastic body such as rubber or thermoplastic elastomer.

The first member 110 comprises a cylindrical shaft portion 111. A shaftportion 111 is formed with a hole 113 penetrating the center of theshaft portion 111 along the axis line O of the shaft portion 111. Bolts(not illustrated) for fixing the shaft portion 111 to the mating member101 are inserted through the hole 113. By fastening the bolts, the shaftportion 111 is fixed to the mating member 101 with both end portions 112of the shaft portion 111 in close contact with the mating member 101.

The second member 120 is a cylindrical metallic member having an innerdiameter larger than the outer diameter of the shaft portion 111. Thesecond member 120 is press fit into the arm 102. The length of thesecond member 120 in the direction of the axis line is shorter than thelength of shaft portion 111 in the direction of the axis line. Thesecond member 120 is arranged at the axis line center of the shaftportion 111, and the vibration-isolation base 30 is bonded to the outerperipheral surface of the shaft portion 111 and the inner peripheralsurface of the second member 120.

The stopper 140 is a plate-like member. The stopper 140 is made of anelastic body such as rubber or thermoplastic elastomer. The shaftportion 111 penetrates the center of the stopper 140. The stopper 140 isarranged between the second member 120 and the mating member 101 with afirst surface 141 of the stopper 140 facing the mating member 101 andthe second surface 142 of the stopper 140, the opposite side of thefirst surface 141, facing the second member 120. The stopper 140regulates the relative displacement of the second member 120 in thedirection of the axis line relative to the first member 110, andmitigates the collision between the arm 102 or the second member 120 andthe mating member 101.

FIG. 9 is a cross-sectional view of the stopper 140 including the axisline O. In the center of the stopper 140, a hole 143 is formed toconnect from the first surface 141 to the second surface 142. The hole143 penetrates the stopper 140. An inner surface 144 of the hole 143 iscircular about the axis line O when viewed from the axis line.

The inner surface 144 of the hole 143 includes a first portion 145connected to the first surface 141, and a second portion 146 positionedbetween the first portion 145 and the second surface 142. The secondportion 146 is smoothly connected to the first portion 145. The firstportion 145 and the second portion 146 are conical surfaces thatgradually increase in span toward the second surface 142. The span D1 ofthe first portion 145 is smaller than the thickness (the diameter D3) ofthe end portion 112 of the shaft portion 111. As a result, the stopper140 is fixed to the shaft portion 111 due to friction between the firstportion 145 and the shaft portion 111.

The span D2 of the second portion 146 is larger than the thickness D3 ofthe end portion 112 of the shaft portion 111. In a state where the shaftportion 111 is inserted into the hole 143, the second portion 146 isspaced from the shaft portion 111. Prior to the shaft portion 111 isinserted into the hole 143, the span of the second portion 146 increasesas it approached the second surface 142. Therefore, the shaft portion111 can be easily inserted into the hole 143 of the stopper 140.

Although the present invention has been described based on embodiments,the present invention is not limited to the above-described embodimentsin any way, and it can be easily understood that various improvementsand modifications are possible within the spirit of the presentinvention.

Although, the shaft portion 13 is formed in a tapered shape and thediameter of the outer peripheral surface gradually decreases toward theend portion 14 in the embodiment, the shaft portions are not necessarilylimited to this. For example, the dimensions of a shaft portion 13 may,of course, be set such that the diameters of the outer peripheralsurfaces of the shaft portion 13 are the same over the entire axis linelength. The shaft portion 13 may be rod-shaped, and the cross-sectionalshape of the shaft portion 13 may be set as appropriate.

Although, the first stopper surface 46, the second stopper surface 47,and the third stopper surface 48 having different heights are formed onthe first surface 43 of the stoppers 40, 60, 70, 80, or 90 in theembodiment, the first surfaces are not necessarily limited to this. Ofcourse, the first stopper surface 46, the second stopper surface 47, andthe third stopper surface 48 may be omitted and the first surface 43 maybe flattened.

Although, in the embodiment, the shapes of inner surfaces 49, 61, 71,81, 91, and 144 of stoppers 40, 60, 70, 80, 90, and 140 are circular orelliptical when viewed from the axis line (in the plan view), the shapesof inner surfaces are not necessarily limited to this. For example,polygons, such as a rectangle and a star polygon, can be adopted as ahole shape of a stopper in the plan view. The spans of the first portionand the second portion in the stopper at this time are the length of theshortest line segment of the line segment obtained by cutting a straightline passing through the center of hole (the axis line O) by the innersurface of the hole in the plan view of the stopper.

Although, in the embodiment, the stoppers 40, 60, 70, 80, 90, 140 ismade of an elastic body such as rubber or thermoplastic elastomer, thestoppers are not necessarily limited to this. The stopper may, ofcourse, be formed by embedding a reinforcing member made of material,such as metals or synthetic resins, in an elastic body. The sizes andshapes of the reinforcing members may be set as appropriate according tothe size and shape of a stopper.

Each of the embodiments may be modified by, for example, adding a partor a plurality of parts of the configuration of another embodiment tothe embodiment, replacing the part or a plurality of parts of theconfiguration of the embodiment.

For example, the stopper of the vibration isolator in the first to thefifth embodiments can, of course, be adopted for the stopper of thevibration isolator in the sixth embodiment. Similarly, the stopper ofthe vibration isolator in the sixth embodiment can, of course, beadopted for the stopper of the vibration isolator in the first to fifthembodiments. In addition, the step 51 can be provided between the firstportions 82, 145 and the second portions 83, 146 in the inner surface 81of the hole 45 of the stopper 80 in the fourth embodiment or the innersurface 144 of the hole 143 of the stopper 140 in the sixth embodiment,or the shape of the second portion 93 of the stopper 90 in the fifthembodiment can be changed to the shape of the second portion 83 of thestopper 80 in the fourth embodiment.

Although, a vibration isolator for a motor vehicle has been described inthe embodiment, the present invention is not necessarily limited tothis. The present invention can also be applied to a vibration isolatorused for, such as motorcycles, railway vehicles, and industrialvehicles. The vibration isolator 10 is not limited to an engine mountfor elastically supporting a power unit such as an engine, and can beapplied to various types of vibration isolator such as a body mount, asub-frame mount, and a differential mount.

What is claimed is:
 1. A vibration isolator comprising: a first memberincluding a shaft portion extending along an axis line, an end portionof the shaft portion being fixed to a mating member; a second memberspaced from the first member and at least a portion of the second memberspaced from the shaft portion in the direction perpendicular to the axisline; a vibration-isolation base made of an elastic body connecting thesecond member and the first member; and a stopper made of an elasticbody having a first surface, a second surface and a hole connecting thefirst surface and the second surface; the stopper arranged in a statewhere the shaft portion of the first member is arranged in the hole withthe end portion facing the mating member, and arranged between thesecond member and the mating member with the first surface facing themating member and the second surface facing the second member, and aninner surface of the hole of the stopper, prior to the shaft portion isarranged in the hole, including: a first portion having a span smallerthan the thickness of the end portion of the shaft portion; and a secondportion arranged between the first portion and the second surface,wherein a span of the second portion is greater than the span of thefirst portion.
 2. The vibration isolator according to claim 1, whereinthe first portion is in contact with the shaft portion when the shaftportion is arranged in the hole.
 3. The vibration isolator according toclaim 2, wherein the first portion includes the entire periphery of theinner surface.
 4. The vibration isolator according to claim 1, whereinthe stopper has a convex portion raised in the axial direction from atleast a portion of the first surface around the hole, and the firstportion includes inside the convex portion.
 5. The vibration isolatoraccording to claim 4, wherein the stopper includes a step between thefirst portion and the second surface, the second portion is disposedbetween the step and the second surface and spaced from the shaftportion when the shaft portion is arranged in the hole.
 6. The vibrationisolator according to claim 1, wherein, prior to the shaft portion isarranged in the hole, the span of the second portion is greater thanthickness of the end portion of the shaft portion.
 7. The vibrationisolator according to claim 1, wherein, prior to the shaft portion isarranged in the hole, the span of the inner surface is increased fromthe first portion to the second portion.